SpaceX has revealed one of its next-generation rocket engines has exploded during a test.

The explosion on Sunday involved the company's Merlin engine, nine of which power its Falcon 9 rocket, during what the company called a 'qualification test.'

No one was injured, and the company said it is 'now conducting a thorough and fully transparent investigation of the root cause' of the explosion.

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A Merlin engine similar to the one that exploded being tested at SpaceX's Rocket Development Facility in McGregor, Texas

THE MERLIN ENGINE

The Merlin engine that powers the first stage of Falcon 9 is developed and manufactured in-house by SpaceX.

Burning liquid oxygen and rocket-grade kerosene propellant, a single Merlin engine emits 845 kilonewtons (190,000 pounds) of thrust at liftoff, rising to 914 kilonewtons (205,500 pounds) as it climbs out of Earth’s atmosphere.

Merlin’s thrust-to-weight ratio exceeds 150, making the Merlin the most efficient booster engine ever built, while still maintaining the structural and thermal safety margins needed to carry astronauts.

'SpaceX is committed to our current manifest, and we do not expect this to have any impact on our launch cadence,' the firm said.

A SpaceX spokesman told the Washington Post the engine that exploded was a new engine that hasn't yet flown, although is is believed is was scheduled for launch late next year.

Testing on the engine, known as the 'block 5' version of the engines in the Falcon 9, will be suspended while the company looks into what went wrong.

The company will also start repairing the test bay the engine exploded on, which should take two to four weeks to complete, according to The Verge.

In 2015, SpaceX's Falcon 9 rocket exploded a couple of minutes after lifting off from Cape Canaveral en route to deliver cargo to the International Space Station.

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Then, in September 2016, another Falcon 9 blew up, this time while on the launchpad as it was being fueled ahead of an engine test fire, and no one was hurt.

The setback comes as SpaceX is having a record-setting year.

The company has launched 16 times successfully this year.

That's double last year's count, and 2017 still has two months remaining.

SPACEX'S 2016 EXPLOSION

Last year a SpaceX Falcon 9 rocket suffered a catastrophic explosion on the Cape Canaveral launch pad during a routine pre-launch check.

The blast, which shook buildings and windows miles away, occurred shortly after 9am and destroyed Facebook's $200million Amos-6 satellite that was set to launch on Saturday morning aboard the reusable rocket.

Billionaire SpaceX CEO Elon Musk said the cause of the massive blast - which caused no injuries - is still unknown as the accident throws into question the future of his program of subcontracting his 'reusable' and 'recycled' rockets to NASA.

The satellite would have opened up free internet to more than 14 countries in Africa to serve the most populated areas more efficiently.

Facebook founder Mark Zuckerberg, who confirmed that the company's satellite was destroyed in the huge blast, called it 'deeply disappointing.'

The unmanned Falcon rocket blasted off from Florida's Kennedy Space Center, hoisting a communications satellite for the South Korean company KT SAT.

This newest Koreasat will replace a failed satellite launched in 2006, and serve both Asia and the Middle East.

Once separated, the 15-story first-stage booster flew to a floating platform in the Atlantic and landed upright.

The TV link of the touchdown was lost.

But SpaceX confirmed success despite the choppy seas and some flames shooting from the landed booster.

'A little toasty, but stage one is certainly still intact,' said the launch commentator from company headquarters in Hawthorne, California.

SpaceX expects to reuse the booster to save time and money.

The SpaceX Falcon 9 rocket: A Merlin engine meant for a future mission exploded on sunday

Other rocket makers ditch the boosters at sea following orbital missions.

The company has launched almost every month this year - a personal record - flying Falcons from both U.S. coasts.

Just minutes after launch, the rocket separated and the tall portion, called the first stage, fired its engines and maneuvered its grid fins to guide itself back to an upright landing on an ocean platform.

Less than nine minutes after takeoff, the scorched rocket touched down on a droneship marked with an X and labeled 'Of Course I Still Love You.'

So far, the company has managed to land more than a dozen rockets after take-off, whether on solid ground or floating ocean platforms.

The goal is to save money and eventually bring down the cost of space travel.

SPACEX'S CHECKERED (AND EXPLOSIVE) HISTORY

Founded in 2002 by PayPal founder Elon Musk, SpaceX has been one of the driving forces behind the efforts by commercial companies to venture into space.

Previously the domain of government-sponsored national agencies like Nasa and Russia's Roscosmos, launching spacecraft into orbit was seen as being prohibitively expensive.

SpaceX, however, became the first privately funded company to launch a rocket powered by liquid-propellant into orbit in 2008 with its Falcon 1.

It later became the first to launch, orbit and recover a spacecraft.

With the end of the Nasa's Space Shuttle program, SpaceX has also stepped in to allow the US to continue to send supplies to the International Space Station.

In 2012 the company was the first private firm to send a spacecraft packed with cargo to resupply the space station.

This year alone it has achieved eight launches carrying supplies to the ISS and a number of satellites into orbit.

But SpaceX's journey has been hit with setbacks and problems.

Perhaps its worst accident to date occurred on June 28 2015 one of its Falcon 9 rockets carrying an unmanned Dragon capsule filled with cargo for the ISS exploded just minutes after launch.

An investigation into the explosion revealed a failed strut on the helium pressure vessels broke as it accelerated out of the atmosphere, allowing a catastrophic escape of gas.

Part of SpaceX's model for reducing the cost of space travel is to reuse its rockets.

But this has been beset with a series of accidents that saw the rockets topple over and explode during these landing attempts.

It lost two rockets after they failed to land safely before it managed to successfully land the first stage booster at Kennedy Space Centre on December 21 2015.

Freezing fog that caused a landing leg to fail to lock caused another rocket to topple over on a barge in January 2016 on landing.

Since then the company has managed to land four of its Falcon 9 launch rockets on floating barges at sea.

But on 15 June this year another of its rockets toppled over and was destroyed after managing to touch down on a barge.

The company has also had problems while in orbit.

In March 1 2013 a Dragon spacecraft suffered thruster issues due to a blacked fuel valve leaving it unable to properly control itself before docking with the ISS.

On this occasion engineers were able to remotely clear the blockages and the craft docked with the ISS one day later than scheduled.